Electrical contactor



Patented Nov. 21, 1939 UNI-TED STATES PATENT OFFICE 2.1m ELECTRICAL ooN'rAc'roa James P. Burke, Knoxville, Tenn.

Application January zr, 193s, sensi No. 181,143

This invention relates to tips for spot welding machines and other types of electrodes or contactors which are subjected to operating pressures.

In spot welding machines, for instance, relatively movable electrodes are adapted to be separated to receive overlapping pieces of metal therebetween. When the electrodes are forced toward each other and against the pieces a current flows from one electrode to the other and hence through the work pieces. The temperature of the pieces is raised to the melting point and the pieces are thus fused together. The electrodes are therefore called upon to perform several duties: they must maintain the work pieces in firm engagement with each other and they must each firmly contact the work pieces in order to establish the electrical path without arcing at their contact with the work, these two 20 requirements necessitating the application of substantial pressure urging the electrodes toward each other. A further duty of the electrodes is to provide the best possible path which is commercially possible between the electrodes 25 which necessitates the use of some relatively soft metal such as copper or aluminum. The sum of these requirements is that a soft metal is subjected to substantial pressures while in a rather highly heated condition with the result that the contact points, known as tips, spread rather easily and must be filed down after short periods of use. It is the primary object of this invention to provide a contact point or tip made of good conductive material, such as copper or aluminum, and to provide a re-enforcing means therefor of such nature that this spreading and consequent rapid deterioration under filling will be overcome to the extent of very materially prolonging the lives of these tips Without interfering with their electrical conductive properties.

More specifically, it is an object of the invention to provide a retaining wall or band of metal of high tensile strength as a means for preventing spreading of the tip, the retaining wall being preferably of very thin cross-section and also, preferably, incorporated in the tip.

Other objects and advantages will hereinafter become more apparent as reference is had to the accompanying drawing wherein:

Fig. 1 is a longitudinal diametric section through a tip blank which is formed as a rst step in the manufacture of a tip, I

Fig. 2 is a view similar to Fig. i with the re`- taining wall applied,

Fig.3isavie'wsimilari:4.11"ig.2showingthe= tip completely formed,

Figs. 4, 5, 6, 7 and 9 are longitudinal diametric sections each illustrating modined forms of tips, and

Fig. 8 is a separate longitudinal diametric ,section through the type of retaining wall illustracted in Figs. 1 and 9.

More specifically, I illustrates a tip blank which has a generally cylindrical main body l0 portion the upper end of which is adapted to be inserted in a suitable holder of a spot welding machine and the lower end of which tapers at 2 into a cylindrical end portion 3. Around the end portion 3, I piace a band 4 of metal of 1I high tensile strength. 'Ihe band l is preferably quite thin and is preferably applied by electrolysis in order to provide a good conductive contact. Chromium lends itself to such application and may be suitably applied, say, to a thickness of ve to twenty thousandths of an inch.

A further layer of copper or other suitable material 5 may then be applied as by dipping or molding for purposes of strength, and the tip is then ready for use. 2

In operation, when pressure is applied by the spot welding machine, the tendency of the metal enclosed by the band 4 to expand is overcome and the tip may therefore be used for long periods of time.

In Fig. 4 a tube 8 of chromium or other material of high tensile strength encircles a solid cylinder 1 of copper or equivalent conductive material, and a body of copper or equivalent material 8 encircles the tube 8 thus giving the tip 35 strength and proper shape.

In Fig. 5 the retaining wall 9 tapers inwardly at its upper end, the object being to prevent a flowing of the soft metal I into the wall under high temperature operation.

Fig. 6 shows the simplest form of my invention, a substantially conventional tip II being used and a band i2 of high tensile strength such as steel, chromium or the like being slipped over the tapered lower end thereof, or plated thereon. 45

Fig. 7 illustrates a modication of Figs. 1, 2 and 3 wherein the retaining wall la is turned or flared outwardly at its upper end I3, the copper la tapering to the periphery of the rim I3 at I4 and the additional copper I5 being. added as a 50 stiifener.

Fig. 9 illustrates a body portion I5 of conventional shape andpreferably made of aluminum. A hole Il is then drilled axially thereof.

A small cylinder of copper I1 is provided and 55 plated with a band I8 oi' chromium or equivalent material andthe composite cylinder is then driven into the opening I8.

'I'his invention may be developed within the g scope oi' the following claims without departing from the essential features of the said invention and it is desired that the specification and drawing be read as being merely illustrative and not in a limiting sense, except as necessitated 10 by the prior art.

What I claim is:

1. An electrical contactor comprising a main body portion composed of'a metal oi' high electrical conductivity, a retaining wall composed u oi a metal oi' high tensile strength encompassing a portion of said main body portion, and a portion of high electrical conductivity encompassing said wall of high tensile strength.

2. An electrical contacter comprising a main n body portion composed o1' a metal of high electrical conductivity, a retaining wall composed of a metal of high tensile strength encompassing a portion of said main body portion, said wall being parallel to the direction of current ow through g5 said body portion, and a portion of high electrical conductivity encompassing said wall of high tensile strength.

3. A spot welding tip composed of a metal body of high electrical conductivity and a stiftener composed of metal oi' relatively high tensile strength imbedded in said body and residing parallel to the flow of current through said body.

4. A spot welding tip composed of a aoi't metal body having a tube of metal oi -relatively high tensile strength imbedded therein concentric with said body and permanently bonded to a portion thereof.

5. A spot welding tip composed of copper having a tube of chromium incorporated therein and concentric with the axis thereof.

6. A spot welding tip composed of copper having a tube of chromium incorporated therein and extending the entire length thereof.

7. A spot welding tip composedV o1' copper having a tube of high tensile strength imbedded therein and extending axially inwardly from the contacting point thereof and terminating at its inner end in a converging upper end portion, said copper being shaped to engage the inner and outer surfaces of the converging tube portion to retain said tube within the copper.

8. The method oftv making spot welding tips which consists in providing a blank of metal having high electrical conductivity, in covering a portion of said blank with a sleeve oi' relatively high tensile strength and in covering said sleeve with metal of high electrical conductivity.

9. The method of making spot welding tips which consists in providing a solid bar of copper, in chromium plating the sides of said bar, and in covering said chromium with copper.

JAIWES P. BURKE. 

